Oliver Wendell Holmes Jr. …

was born on this date in 1841. Three times wounded in the Civil War, Holmes survived to become a prominent legal scholar, Chief Judge of the Massachusetts Supreme Court, and Justice of the United States Supreme Court, 1902-1932. He is considered one of the greatest of the Supreme Court justices.

But the character of every act depends upon the circumstances in which it is done…. The most stringent protection of free speech would not protect a man in falsely shouting fire in a theatre and causing a panic. It does not even protect a man from an injunction against uttering words that may have all the effect of force…. The question in every case is whether the words used are used in such circumstances and are of such a nature as to create a clear and present danger that they will bring about the substantive evils that Congress has a right to prevent. It is a question of proximity and degree.
Justice Oliver Wendell Holmes, Schenck v. United States, Baer v. United States, 249 U.S. 52 (1919).

But when men have realized that time has upset many fighting faiths, they may come to believe even more than they believe the very foundations of their own conduct that the ultimate good desired is better reached by free trade in ideas—that the best test of truth is the power of the thought to get itself accepted in the competition of the market, and that truth is the only ground upon which their wishes safely can be carried out.
Justice Oliver Wendell Holmes, dissenting, Abrams et al. v. United States, 250 U.S. 630 (1919).